Over half of the district comprises less than 10% indigenous vegetation cover, with some areas containing less than 0.5%. However, within our existing fragmented remnants are many rare and threatened species which are not represented in the New Zealand protected areas network.
The Waimakariri district comprises a range of natural habitats including important bush areas, foothills, alpine and high-country areas, dryland shrublands and tussock lands, braided rivers and salt marsh lagoons.
Waimakariri District has diverse terrestrial and aquatic habitats covering the montane hills and basins in the northwest to the coastal wetlands and estuaries. Indigenous biodiversity includes both vegetation and non-vegetated habitats (such as rocky outcrops) and the plant and animal species (common or threatened) supported by them.
The geology, soils, climate and historic and current land/water uses shape the indigenous biodiversity we see today. They influence what grows where, how much there is, and how healthy it is.
Prior to European settlement, the hills would have supported forest, shrublands and, at higher altitude, grassland and rock habitats while the plains were predominantly covered by dry grasslands and shrublands with areas of forest (such as the extensive Oxford Forest). East of roughly the current line of State Highway 1 there were extensive wetlands and sand dunes, with estuarine habitats around Te Aka Aka (Ashley/Rakahuri Estuary). All have been modified by historic and ongoing land and water uses and by introduced plant and animal species, such as gorse and possum.
New Zealand has been divided into a number of Ecological Districts (EDs), based on their shared ecological features. Waimakariri District falls into parts of five EDs. There are smaller areas or zones within them reflecting local conditions. Environment Canterbury mapped these zones as part of preparing guidance for restoration planting. The zones show areas with similar soils and climatic features, and to which particular groups of indigenous plants should be best suited. The boundaries between these zones is not a clear line, with some features grading across them.
High country and foothills
Along the Puketeraki Range on the western edge of the District are alpine and sub-alpine habitats. Areas of rocks, scree and sub-alpine shrublands, tall tussock lands, and herb-fields support a range of native plants and animals, many of which are rare and threatened. Insects including cicadas, grasshoppers, moths and butterflies as well as the alpine scree weta are found here. Lees Valley is a mid-altitude basin lying between the Puketeraki Range of mountains and the foothills. Although much of the valley bottom is farmed, there remain large important wetlands associated with the Ashley/Rakahuri and Okuku River systems. There is also a protected area of unusual dry shrubland/grassland. The lower slopes around the Valley and extending onto the eastern slopes above the Plains, are extensive native beech forests (mountain and black with occasional red beech). Patches of mixed beech-podocarp forest remain, and shrublands with common species such as Coprosma species, broadleaf, five-finger and mahoe. The Ashley and Okuku Gorges support unusual rocky, dryland plant communities and in some parts are inaccessible to grazing animals. At the northern end of the District, around Mt Grey, red beech is extensive.
In the View Hill area there are important remnants of the podocarp forest and wetlands that would once have been more extensive. Here are found the rare Canterbury mudfish; while the rocky outcrops of limestone along the foothills, such as at Whiterock, support plants that prefer calcareous soils.
Kea, NZ pipit and NZ falcon may be seen throughout the higher parts of the District and geckos and skinks can be found in the less disturbed shrublands and sub-alpine areas.
We can divide the plains into two at around the 150m contour reflecting the gradient of climate and soils from west to east; in the “High Plains” there is higher rainfall than further east and slightly deeper soils over the glacial outwash gravels. Less than 10% of the former native vegetation cover remains in this area so that any native plants, and the native animals they support are highly valued. Scattered plants of flax, kowhai and cabbage trees remain alongside rivers and streams. Burnt Hill is a small volcanic outcrop with dry grassland and shrubland vegetation. Eyrewell Scientific Reserve is one of the largest areas of dry shrubland (kanuka) in the District. It is valuable for not only the stand of kānuka, but for the intact soils, mosses, lichens and herbs; and the lizards and insects found there. Fencing and planting with native species by rural landowners is starting to restore the indigenous vegetation cover in this area.
Lying between the 150m contour and SH 1, the drier Low Plains also have less than 10% of their former native cover; restoration planting associated with farming and urban developments is starting to redress the loss. Remnant kānuka plants and communities remain on the river terraces and along roadsides while kowhai, flax and cabbage trees are associated with waterways. Scattered wetlands occur, often on private land, and these are valuable habitats for invertebrates, tuna/eels and some common native fish. They are also important in the storage of water during rain events. Matawai Park in Rangiora has been planted with examples of local native vegetation types, starting in 1970 and with the wetlands and waterways around Northbrook reserve provides an illustration of former cover.
The area roughly between SH1 and the sea is influenced by the sandy soils, the emerging groundwater and coastal climate. Between the Waimakariri River and the Ashley/Rakahuri River mouths, is a band of low lying sand dunes and wetlands. As part of the development of Pegasus Township lakes and wetland enhancement was carried out and now most of the area between the river mouths is managed as part of Tūhaitara Coastal Park with extensive planting and mudfish management as well as pest and weed control. Wetlands hold significant ecological and cultural value. Wetlands act as kidneys of the earth. They cleanse the water that enters them by trapping sediment and removing contaminants/nutrients. As well as the Canterbury Mudfish, they are home to animals such as eels, Australasian bittern and the Royal spoonbill. They also are home to plants like raupo, harakeke, Juncus and toetoe. Lakes are an important feature of the landscape in the Waimakariri district, providing habitat for many fish and birds. Unfortunately they are vulnerable to rapid contamination and eutrophication, as they take longer to flush than flowing waterbodies.
The Ashley/Rakahuri and Saltwater Creek estuarine areas are listed as meeting the criteria for wetlands “of international importance”. Unusual sand dune plants such as matagouri and four square rush are found in the coastal band. Estuaries are ecologically diverse systems that are a mixture of fresh and saltwater. Water circulates in and out due to the flow of freshwater, tides and waves. This allows them to trap and transport nutrients and sediment. They play a very important role for migratory birds, fish and crustaceans. They provide food, breeding grounds, and a place to rest. In the Waimakariri District.